Method of refining oil with a solvent



W. E. SKELTON ETAL Filed Sept. 30, 1947 .Flrlrahllln Ilnlllllul METHOD OF REFINING OIL WITH A SOLVENT M MOT 5 mNL y NPM E w25 N m55.

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@w of Patented Dec. 19, 1950 UNITED STATES PATENT OFFICE METHOD F REFINING OIL WITH A SOLVENT William E. Skelton, Beacon, and George B.

Arnold, Glenham, N. Y., assignors to The Texas Company, New York, N. Y., a corporation of Delaware Application September 30, i947, Serial No. 777,071

8 Claims.

. presence of a small amount of water and under conditions effective to form extract and raffinate phases respectively. The rainate phase comprises non-aromatic or relatively insoluble constituents of the oil mixed with a small proportion of the solvent and water. The extract phase comprises the relatively aromatic and naphthenic constituents of the oil dissolved in the main body of aqueous solvent.

The extract and raiiinate phases are separately subjected to azeotropic fractional distillation so as to effect separation of solvent from the oil. The invention contemplates supplying suicient steam or water to the fractionating zone in which the raffinate phase is distilled to form a ternary water-oil-solvent azeotrope with all or substantially all of the solvent present in the raffinate phase mixture. In the distillation of the extract phase mixture, sufficient steam or water is added to the fractionating zone to form a ternary solvent-water-oil azeotrope either with all or with a major portion of the extract oil present in the extract phase mixture.

. The resulting distillates are separately cooled, condensed and subjected to settling, so that they separate into oil-rich, Water-rich and solventrich liquid layers respectively. The oil-rich liquid from each settling zone is separately subjected to azeotropic distillation in the presence of steam or water so as to form in each case a ternary solvent-oil-water azeotrope with all of the residual solvent present in the oil-rich liquids. The resulting ternary azeotrope distillates are advantageously recycled to the previously mentioned settling zones. In other words, that derived from the raiiinate phase mixture is recycled to the settling zone, operating in conjunction with the ralinate phase fractionator while that derived from'the extract phase is recycled to the settler which operates in conjunction with the extract phase fractionator.

If desired, the oil-rich phase obtained from the rainate can be recycled, all or in part, through pipe I3A to the tower l.

vAccording to a modification of the invention,

the distillate discharged from the raffinate phasel fractionating zone, instead of being separately cooled and condensed, can be commingled with the distillate from the extract phase fractionating zone, and the resulting mixture treated as' already described.

The oil-rich layers previously referred to are drawn off and passed to a fractionator wherein"l residual solvent is stripped from the water, and

the so-recovered solvent recycled to the extrae?y tion Zone. If desired, a portion of the 'Water-rich liquid removed from each settling zone may be` recycled as reiiux to the raiinate phase and ex` tract phase fractionating zones respectively to supply at least in part the water required for azeotropic distillation. v

The solvent-rich layers previously referred to are drawn off and recycled to the extraction zone.

According to one modification, the furfural-rich liquid drawn off from the settling zone operating in conjunction with the extract phase fraction-` ator is recycled to the extract phase fractionator.`

The invention thus involves recovering solvent as a distillate from the rainate oil and as an oil-free or substantially oil-free liquid residue from the extract phase.

The invention is particularly applicable to the solvent treatment of low boiling oils, such as-l kerosene or fractions of petroleum boiling in the` range of about 300 to 650 F. (ASTM), and com,Y prising constituents which form relatively low boiling azeotropes with the solvent and water. A' feature of the invention is that only a small portion of the solvent is vaporized in recovering the solvent from the raflinate and extract oils, so that considerable saving in heat is realized over a process involving recovery of the solvent by simple distillation. In addition, the solvent is subjected to less severe temperatures and, therefore, subject to less decomposition. In order to illustrate the invention in mor detail, reference will now be made to the accompanying drawing comprising a flow diagram of the process as applied to the treatment of kero sene derived from California crude. The feed oil has an API gravity of about 40.4 and has an ASTM boiling range as follows:

IBP `332 10a7 365 20% 377 50% 414A 4 82 E. P. 520

As indicated in the drawing, the feed oil is conducted from a source not shown through a pipe I and heat exchanger 2 to the lower portion of an extraction tower 3 of conventional type.

The feed oil rises through the packing of the tower countercurrently to a stream of solvent liquid introduced to the upper portion of the tower through a pipe 4. The solvent comprises furfural and may contain water and oil as a result of previous use in the process. It thus contains about 15.0% oil and 3.0% water. It is introduced to the tower in the proportion of about 1 volume of solvent to 2 volumes of oil. The temperatures of entering streams of oil and solvent are regulated, so that the temperature at the bottom of the tower is maintained at about 100 F., while the temperature at the top is main tained at about 150 F.

Under these conditions, extract and raffinate phases form.. The rainate phase comprises oil amounting to from about 60 to 80% by volume of the feed oil. rlhe rafnate phase is continuously removed from the upper portion of the tower 3 through a pipe 5 and heat exchanger 6 to a fractionator l. Heat may be supplied to the bottom of the fractionator either with open steam, a closed heating coil, or a combination of both. will be mentioned later, provision is made for supplying reflux liquid to the top of the tower.

Suil'cient water is introduced to the tower either I inthe form of steam or water redux or both steam and reflux' liquid to form the ternary water-oilfurfural azeotrope with all of thefurfural present i'rr the raffinate phase feed. The top of the tower maintained at a temperature of about 205 to 250 F., and the bottom at a temperature of about 250' to 500 F., so that the solvent is completely or substantially completely distilled from the ranate oil, the solvent-free oil being discharged through pipe 8'. Actual tower temperatures will depend upon the true boil-ing point curve of the oil The distillate comprisingsolvent, water, and a small amount or oil` is moved through pipe 9 into condenser I to a settling chamber II. The settler is maintained at a temperature of about '70 to 150- 2 F., and. the condensate separates into oilrich, water-rich, and solvent-rich liquid layers respectively. The composition. of the'th-reelayers is approximately as follows:

yrurfurai 011 Water Per Cent Per Cem Per Cent Oil-richlayer 4- 6' 94-96 0.1-0.2 Water-rich layen-.. 6- 7 0.1 94-93 Furural-rich layer 80-82 15 3 The solvent-rich liquid isv continuously drawn off through pipe. I2 which communicates -with vpipe 4 by which this liquid is recycled to the extraction tower 3.

The oil-rich liquid is drawn off from. the top of the settling. chamber through a pipe I3 and passed tov a. secondary fractionator lwherein it is subjected. tol azeotropic distillation, suiiicient water being injected into the fractionator either in the form of open steam or water reflux to form the ternary azeotrope of furfural, oil, and water, the operation of this fractionator being conducted so as. to'eiect recovery of raffinate oil from the oilrich liquid; The recovered oil' is discharged through pipe I 6', while the distillate from this fractionator is recycled through a pipe I'I to the settling chamber II.

The recovered oil has approximately the fol1ow ing characteristics:

Gravity A. P. I 42.0 Aniline point 136.5 Sulfur, per cent 0.01 Refractive index 1.4.45

The extract phase collecting in the bottom of the extractionitower 3 is continuously drawn off through pipe 26 and exchanger 2l to an extract phase fractionator 22. This fractionator, like fractionator "l, is provided with means for supplying heat to the bottom thereof, either in the form Sulfur, per. cent of open steam or a closed heating coil or both, provision being made also for the introduction of reflux liquid. Suiiicient water is injected through the fractionator to; form a ternary furfuraloil azeotrope with all or a desired portion of the extract oil. The extract oil is thus removed in the form of a distillate while oil-free solvent or solvent containing a predetermined quantity of extract oil is discharged as a residualY liquid through pipe 23 for recycle through pipe 24 to the extraction tower.

The distillate is drawn off through pipe 25 and condenser 26 toa settler 21 maintained at about 70 to 150a F., so that Separation into oil-rich, water-rich, and solvent-rich liquid layers occurs.

The solvent-rich liquid is drawn oir through pipe 28, and, according to a preferred mode of operation, is recycled through pipe 201 to the fractionator 22. All o1' a portion of it may be so recycled. On' the other hand, all or a portion of this' solvent-rich liquid may be conducted through pipes 30 and 3| for return through pipes 24 and 4 to the extractor.

The oil-rich liquid accumulating in the top of the settling chamber 2 is drawn off through pipe 33 to another secondary fractionator 3d operated in a manner somewhat similar to the fiactionator I5, so that all of the solvent is azeotropically distilled from the extract oil. The resulting distillate is recycled through pipe 35 to the settler 21, while the extract eil product is discharged from the bottom of the ractionator through pipe 31. This extract oil is of the following approximate character:

Gravity A. P. I i 32.7 Refractive index 1.4895

Thek water-rich liquid layers accumulating in the mid-portions of settlers III and 2l are drawn off through pipes 40 and 4I respectively and conducted through pipe 42 to a tertiary fractionator 43. This water-rich liquid com-prises about 94% water, theV remainder being chiefly furfural with 0.1 to 2% oil. yThe solvent is distilled? from the bulk of the water in the fractionator 43, and the resul-ting distillate conducted' through pipe 4.4 and condenser 45 to a settler i6 wherein separation into water layers and solvent layers respectively occurs. All or a portion of the water layers may be recycled while the solvent layer is drawn off through. pipe communicating with pipe 3| by which it is returned to the extractor 3.

As indicated in the drawing', a portion of the water-rich liquid owing through pipe 40 may be diverted through a pipe 6'0 as reflux liquid'. to the fractionator lI, while a portion ofthe water.- rich liquid from pipe 4I may be diverted through a pipe 6I as reflux. to the fractionator 22..

If desired, and especially when handling gas oils, the distillate from the fractionator 1' may be diverted from pipe 9 through a branch pipe 9A and thus passed to the condenser 26 wherein lt merges with the distillate from fractionator 22;/ In this way, and with a small sacrifice in raffinate oil yield, the settler ll and fractionator l can be omitted.

Also, instead of employing the fractionators I5` and 34, the oil-rich liquids nowing through .pipes I3 and 33 may be washed either separately or" in the presence of each other with a liquid medium and under conditions effective to extract the residual solvent from the oil. The extracted re'- sidual solvent can be recoveredfor reuse. 'For example, these oil-rich liquids can be subjectedto contact with water at an elevated temperature of about 200 to 300 F., so that furfural is selec.- tivelydissolved from the oil by the-water. The resulting water solution can then be subjected .to countercurrent contact with a stream of feed oil at a temperature of about 100 to 130 Faso as to extract the dissolved furiural from the water and the resulting solution of furfural in feed oil is thenv passed to the extractor 3- f If` desired, provision may be made forrecycling' at least a portion of the oil-rich liquid from the settler Il to the fracticnator l. indicated, the fractionator 22 may be operated to etect partial stripping of extra-ct oil from the furfural. Thus, it may be operated so that the furfural stream removed through pipe 23 retains4 0 to` 10% by volume of extract oil, depending upon the amount of such extract oil which it is,

desired to recycle to the extraction tower 3. In

the` treatment of light feed oils, the solubility in the solvent may be so great as to. require operation at relatively low temperatures in order to obtain a` satisfactory raffinate oil yield.

While the treatment of kerosene has been specically referred to in connection with the drawing, nevertheless, it should be understood that the process is applicable to the treatment of virgin and lcracked gas oils and also to the treatment of kerosene containing, usually in small amounts, constituents having a true boiling point lower than, or in the same-boiling, range as that.. of the solvent used. In general, ithas application to the treatment of hydrocarbonmixtures having an A. S. T. M. boiling .range .of, about:325. to 625 F. I Alt is also contemplated that it has application to the treatment of oils derived from animal and vegetable sources. tions of temperature and solvent dosage may vary from those specifically mentioned, depending on the character of the feed oil undergoing treatment andthe degree of fractional separation desired in the extraction tower 3.

The invention is particularly concerned with the use of relatively high boiling organic solvent liquids whichare miscible, at least to some extent with water, and with which constituents ioflthe oil `feed in the presence of. water form az'eotropes. Selective solvents other than urfural vmay be used. They may include. other derivatives of the furan group and other aldehydes' such as benz"- aldehyde,nitrobenzene andketoneaetc,

Obviously, many..modifications.4 and variations of the invention as above set forth may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

We claim:

1. In the solvent reiining of feed oil of the class consisting of kerosine and low boiling gas oil and containing at least a small pro-portion of constituents having true boiling points in the .As previously i Specific condii range of the solvent boilingv temperature and4 below wherein the feed oil is subjected to convent from the oil for reuse in the extraction zona,

the method comprising distilling from said rafnate phase in the presence of steam a ternaryY azeotrope distillate containing substantiallyall ofthe solvent in the removed raffinate phase and.

leaving a substantially solvent-free ranate oil,` discharging raffinate oil, separately distilling from said extract phase in the presence of, steam a ternary azeotrope distillate containing at least the bulk of the extract oil in the removed extract, phase and leaving the bulk of the solvent contenti of the removed extract phase as a residual liquid,- fraction, recycling resulting residual fraction toI the extraction Zone, separately subjecting each? of said distillates to substantially complete con;v densation, separately subjecting the resulting condensates to settling at a temperature of about to 150 in separate settling Zones under con-v ditions such that there is no substantial vaporization of water, forming in each settling Zone, oilrich, water-rich and solvent-rich liquid layers respectively, separately withdrawing liquid from` each layer, recycling withdrawn solvent-rich liquids from both 'settling zones to said extrae-f' tion Zone, separately distilling residual solvent from each of said withdrawn oil-rich liquids, come@ bining said withdrawn water-rich liquids, subjecting resulting combined liquid to a furtherl distillation to remove excess water from residual solvent, discharging resulting aqueous distillate, and recycling resulting residual solvent recovered from the oil-rich liquids and also from the combined liquids to the extraction zone.

` 2. rIhe method according to claim l in which said withdrawn oil-rich liquids are separately-x subjected to azeotropic distillation in the pres.v ence of steam under conditions effective to ob-f tain ternary solvent-oil-water azeotropes as dis-'fv tillates, leaving substantially solvent-free oil asf liquid residues, the resulting residues are discharged and said ternary azeotrope distillates arev condensed and recycled to the settling zones re-A spectively which supply the fractionating zones" from which they are derived.

3. In the solvent refining of kerosene and low'y boiling gas oils containing at least a small pro'-v portion of constituents having true boiling points",

in the range of the solvent boiling temperature and below wherein the feed oil is subjected to contact in an extraction zone with a water miscible organic solvent liquid having selective action as between parafiinic and non-paranic con-v in the presence of water vapor under conditions such that substantially all of the solvent is removed as a solvent-water-oil azeotrope distillate, leaving a primary distillation residue consisting of raffinate oil substantially free from solvent, separately subjecting said extract phase mixture in a primary distillation column to dis tillation in the presence of water vapor under conditions such that substantially all of the extract oil is removed as a oil-water-solvent azeotrope distillate, leaving another primary distillation residue consisting of solvent substantially free from oil, separately condensing said primary azeotrope distillates, separately subjecting resulting condensates to settling in settling zones maintained under conditions such that there is no substantial vaporization of water, forming in each settling zone oil-rich, water-rich and solventrich liquid layers respectively, separately withdrawing liquid from each layer, recycling withdrawn solvent-richk liquids at least in part to said extraction zone, separately distilling residual solvent from said withdrawn oil-rich liquids to recover solvent, recycling resulting recovered solvent` to the extraction zone, subjecting said withdrawn water-rich liquids to further distili lation to strip water therefrom, leaving a residual concentrate of solvent, and recycling said solvent concentrate to the extraction zone.

4. The process according to claim 3 the solvent comprises furfural.

5'. In the solvent rening of kerosene and low boiling gas oils containing at least a small proportion of constituents having true boiling points in the range of the solvent boiling temperature in which and below wherein the feed oil is subjected to contact in an extraction Zone with a water miscible organic solvent liquid having selective action as between paraflinic and non-paraflmic constituents of the feed, extract and raffinate phase `mixtures are formed respectively lean in and rich in said paraiinic constituents, said phase mixtures are separately removed from the extraction zone, and the removed phase mixtures separately treated to recover solvent from the oil for re-use in the extraction zone, the method comprising subjecting said extract phase in a primary distillation column to distillation in the presence oi` water vapor under conditions such that substantially all of the extract oil is removed as an oilwater-solvent azeotrope distillate, leaving a primary distillation residue consisting substantially of solvent substantially free from oil, condensing resulting primary azeotrope distillate, subjecting resulting condensate to settling in a settling zone maintained under conditions such that there is of solvent and recycling said concentrate to said extraction zone.

6. The method according to claim 5 in which-l the,v solvent comprises furfural.

'1. In the solvent refining of kerosene and low boiling gas oils containing at least a small proportion of constituents having true boiling points in the range of the solvent boiling temperature and below wherein the feed oil is subjected to contact in an extraction zone with a water miscible organic solvent liquid having selective action as between parailinic and non parafnic constit-V uents of the feed, extract and raffinate phase mixtures are formed respectively lean in and rich in said paraffinic constituents, said phase mixtures are separately removed from the extrac-l tion zone, and the removed phase mixtures separately treated to recover solvent from the oil for re-use in the extraction zone, the method comprising subjecting said extract phase in a pri mary distillation column to distillation in the presence of water vapor under conditions such that substantially all of the extract oil is removed as an oil-water-solvent azeotrope distil.

late, leaving a primary distillation residue consisting substantially of solvent substantially free from oil, condensing resulting primary azeotrope distillatel subjecting resulting condensate to settling in a settling zone maintained under conditions such that there is no substantial vaporiza` tion of water, forming in said settling Zone a plurality of liquid layers comprising an oil-rich liquid layer containing small amounts of solvent and water, and a water-rich liquid layer contain.

ing small amounts of oil and solvent, separately withdrawing liquid from each layer, distilling residual solvent from said withdrawn oil-rich liquid leaving a residue of extract oil substan` tially free from solvent, recycling so recovered solvent to the extraction zone, discharging said.

residue of oil, subjecting said withdrawn waterrich liquid to further distillation to strip water therefrom, leaving a residual concentrate of solvent, and recycling said concentrate to said extraction zone.

8. The method according to claim '7 in which the solvent comprises furfural.

WILLIAM E. SKELTON. GEORGE B. ARNOLD.

REFERENCES CITED The following references are of record in thev file of this patent:

UNITED STATES PATENTS Number Name Date 2,139,240 McFarland Dec. 6, 1938 2,154,189 Weir Apr. 11, 1939 2,154,372 Bosing Apr. 11, 1939 2,168,570 Kraft Aug. 8, 1939 2,216,933 Atkins Oct. 8, 1940 2,290,636 Deanesly July 21, 1942 2,381,996 Bloomer Aug. 15, 1945 2,419,039 Scarth Apr. l5, 1947 2,465,959 Tindall Mar. 29, 1949 

1. IN THE SOLVENT REFINING OF FEED OIL OF THE CLASS CONSISTING OF KEROSINE AND LOW BOILING GAS OIL AND CONTAINING AT LEAST A SMALL PROPORTION OF CONSTITUENTS HAVING TRUE BOILING POINTS IN THE RANGE OF THE SOLVENT BOILING TEMPERATURE AND BELOW WHEREIN THE FEED OIL IS SUBJECTED TO CONTACT IN AN EXTRACTION ZONE IN THE PRESENCE OF WATER WITH A WATER-MISCIBLE ORGANIC SOLVENT LIQUID COMPRISING FURFURAL HAVING SELECTIVE ACTION AS BETWEEN THE PARAFFINIC AND NON-PARAFFINIC CONSTITUENTS, EXTRACT AND RAFFINATE PHASES ARE FORMED RESPECTIVELY LEAN IN AND RICH IN SAID PARAFFINIC CONSTITUENTS, SAID PHASES SEPARATELY REMOVED FROM THE EXTRACTION ZONE, EACH OF SAID REMOVED PHASES COMPRISING OIL, SOLVENT AND WATER, AND THE REMOVED PHASES SEPARATELY TREATED TO RECOVER SOLVENT FROM THE OIL FOR REUSE IN THE EXTRACTION ZONE, THE METHOD COMPRISING DISTILLING FROM SAID RAFFINATE PHASE IN THE PRESENCE OF STEAM A TERNARY AZEOTROPE DISTILLATE CONTAINING SUBSTANTIALLY ALL OF THE SOLVENT IN THE REMOVED RAFFINATE PHASE AND LEAVING A SUBSTANTIALLY SOLVENT-FREE RAFFINATE OIL, DISCHARGING RAFFINATE OIL, SEPARATELY DISTILLING FROM SAID EXTRACT PHASE IN THE PRESENCE OF STEAM A TERNARY AZEOTROPE DISTILLATE CONTAINING AT LEAST THE BULK OF THE EXTRACT OIL IN THE REMOVED EXTRACT PHASE AND LEAVING THE BULK OF THE SOLVENT CONTENT OF THE REMOVED EXTRACT PHASE AS A RESIDUAL LIQUID FRACTION, RECYCLING RESULTING RESIDUAL FRACTION TO THE EXTRACTION ZONE, SEPARATELY SUBJECTING EACH OF SAID DISTILATES TO SUBSTANTIALLY COMPLETE CONDENSATION, SEPARATELY SUBJECTING THE RESULTING CONDENSATES TO SETTLING AT A TEMPERATURE OF ABOUT 70* TO 150* IN SEPARATE SETTLING ZONES UNDER CONDITIONS SUCH THAT THERE IS NO SUBSTANTIAL VAPORIZATION OF WATER, FORMING IN EACH SETTLING ZONE, OILRICH, WATER-RICH AND SOLVENT-RICH LIQUID LAYERS RESPECTIVELY, SEPARATELY WITHDRAWING LIQUID FROM EACH LAYER, RECYCLING WITHDRAWN SOLVENT-RICH LIQUIDS FROM BOTH SETTLING ZONES TO SAID EXTRACTION ZONE, SEPARATELY DISTILLING RESIDUAL SOLVENT FROM EACH OF SAID WITHDRAWN OIL-RICH LIQUIDS, COMBINING SAID WITHDRAWN WATER-RICH LIQUIDS, SUBJECTING RESULTING COMBINED LIQUID TO A FURTHER DISTILLATION TO REMOVE EXCESS WATER FROM RESIDUAL SOLVENT, DISCHARGING RESULTING AQUEOUS DISTILLATE, AND RECYCLING RESULTING RESIDUAL SOLVENT RECOVERED FROM THE OIL-RICH LIQUIDS AND ALSO FROM THE COMBINED LIQUIDS TO THE EXTRACTION ZONE. 